282 Prof. Norton on Molecular Physics. 



sing currents. But if we suppose that, in the case of steel, the 

 molecular groups are imperfect conductors, the magnetizing 

 force will develope a polarization of the separate molecules ; and, 

 as a consequence, the currents may pass chiefly through their 

 atmospheres, as in the case of electric induction (p. 101). In 

 this state of things, when the force is withdrawn, it does not 

 follow that the magnetic currents will entirely pass off ; for there 

 would apparently be a force in operation which would tend to 

 retain currents of a certain intensity in circulation. This is the 

 mutual action of the contiguous positive and negative sides of 

 two molecules throughout the chain. It would seem that such 

 a circular chain of particles would not, of necessity, attain to a 

 condition of statical polarization, but might reach a dynamical 

 equilibrium in which the impulsive force, from each discharge 

 brought about by the action of contiguous molecules, should 

 restore the polarization lost by the discharge to the next pre- 

 ceding molecule*. 



According to this view, permanent magnetization consists in 

 polarizing the molecules ; and it is this induced state which de- 

 termines and maintains, in opposition to all resistances, currents 

 of a certain intensity. A certain amount of force (" coercive 

 force ") and a certain interval of time are expended in developing 

 this polarization. At the same time it is only when this force 

 is exerted with this result that permanent magnetism can exist. 

 Heat, or a blow, or an electric discharge, by destroying the mole- 

 cular polarization, may demagnetize the bar. It is also to be 

 observed that intense heat may demagnetize a bar, and destroy 

 the susceptibility to magnetism in iron or steel, by breaking up 

 the groups of particles into which the mass is aggregated. 



Diamagnetism. — It has already been intimated that the dia- 

 magnetic state into which certain substances, as bismuth, phos- 

 phorus, antimony, &c, are brought by the action of a powerful 

 magnet, probably consists in the circulation of currents around 

 the compound molecules of the mass in the opposite direction 

 to the inducing current, and that these currents result from the 

 second mode of operation of the external force of the primary 

 current (p. 280). Accordingly, the susceptibility to diamag- 

 netism must arise from a special liability to expansion on the 

 part of the electric atmospheres of the simple molecules, when 

 urged upward by the sethereal pulses that fall upon their central 

 atoms. 



* It is worthy of consideration, whether certain phenomena of luminosity 

 as phosphorescence, heat-lightning, &c, may not have a similar origin, viz. 

 in recurring discharges resulting from a previous molecular polarization, 

 established by an electric discharge through the mass — or from a similar 

 effect produced in a feebler degree by heat or light. 



